plaid screen

[XEROX PARC] A `special effect' that
occurs when certain kinds of memory smashes overwrite the
control blocks or image memory of a bit-mapped display. The term
"salt and pepper" may refer to a different pattern of similar
origin. Though the term as coined at PARC refers to the result of
an error, some of the X demos induce plaid-screen effects
deliberately as a display hack.